Boron tribromide mediated debenzylation of benzylamino and benzyloxy groups

The treatment of 2(or 4)-benzylamino substituted quinolines, 9-benzylaminoacridine, 2-benzylaminopyridine, a 4-benzyloxyquinoline, and an N-benzyloxyamidine with BBr₃ yields the corresponding amino or hydroxy substituted compounds. The scope and limitations of this novel reaction are discussed.     

Synthesis of a cyclic dinuclear organotin carboxylate via simultaneous debenzylation and decarbonylation reactions: X-ray crystal structure of [(PhCH2)2{O2CC6H4{N(H)N(C6H3-4(O)-5-O)}-o}Sn]2

The complex, [(PhCH₂)₂{O₂CC₆H₄{N(H)N(C₆H₃-4(O)-5-O)}-o}Sn]₂ (1), is obtained as the exclusive reaction product from the reaction of sodium 2-[(E)-2-(3-formyl-4-hydroxyphenyl)-1-diazenyl]benzoate and (PhCH₂)₃SnCl. The reaction possibly proceeds via Dakin type rearrangements where arylazosalicylaldehyde is oxidized to arylazocatechol, followed by facile Sn-C bond cleavage. Complete assignments were achieved by ¹H, ¹³C, 2D ¹H-¹¹⁹Sn HMQC (¹¹⁹Sn chemical shift), 1D gs ¹H-¹⁵N HMQC (¹J(¹⁵N, ¹H) coupling constant) NMR and ESI-MS. The crystal structure of compound 1 as determined by X-ray diffraction analyses shows a cyclic centrosymmetric dinuclear moiety linked into extended chains by pairs of long Sn?O contacts of approximately 3.2 Å. Two polymorphs were identified and their structures differ primarily in the packing arrangement afforded by the benzyl groups. In one polymorph, when viewed along the Sn?Sn vector, the benzyl groups at each Sn-atom are oriented to form an S-shape, while they form a U-shape in the second polymorph.     

Pinacol Rearrangement of 3,4‐Dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones: An Alternative Pathway to Viridicatin Alkaloids and Their Analogs

3‐Alkyl/aryl‐3‐hydroxyquinoline‐2,4‐diones were reduced with NaBH₄ to give cis‐3‐alkyl/aryl‐3,4‐dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones. These compounds were subjected to pinacol rearrangement by treatment with concentrated H₂SO₄, resulting in 4‐alkyl/aryl‐3‐hydroxyquinolin‐2(1H)‐ones. When a benzyl (Bn) group was present in position 3 of the starting compound, its elimination occurred during the rearrangement, and the corresponding 3‐hydroxyquinolin‐2(1H)‐one was formed. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, ¹H‐ and ¹³C‐NMR spectroscopy, as well as mass spectrometry.     

Reaction of 3‐Hydroxyquinoline‐2,4‐diones with Inorganic Thiocyanates in the Presence of Ammonium or Alkylammonium Ions: the Unexpected Replacement of a Hydroxy Group by an Amino Group

3‐Hydroxyquinoline‐2,4‐diones react with KSCN in the presence of the NH$\rm{{_{4}^{+}}}$ ions to generate 2,3‐dihydro‐3‐thioxoimidazo[1,5‐c]quinazolin‐5(6H)‐ones, 2,3‐dihydro‐2‐thioxo‐1H‐imidazo[4,5‐c]quinolin‐4(5H)‐ones, and products of molecular rearrangement of the 3‐aminoquinolinedione intermediates. Starting compounds with a benzyl (Bn) group at C(3) afford 3‐aminoquinolinediones, even when only AcONH₄ is used. The results of the reaction between 3‐hydroxyquinoline‐2,4‐diones and KSCN in the presence of BuNH₂ show that replacing a OH group with a secondary NH₂ group is also possible.     

Selective debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate

A new debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.     

Selective modification of oleuropein,a multifunctional bioactive natural product

Oleuropein is the major phenolic compound extracted from olive leaves and it is also present in olive fruits and virgin olive oil. It has already demonstrated a wide range of pharmacological activities, but new derivatives have to be designed in order to obtain useful Structure–Activity Relationships for this family of products, as well as new analogs with improved and/or different biological properties. However, taking into account the multiple OH groups (catechol and sugar) present in oleuropein, the selective modification of this natural product is a challenging problem. In this paper, we present an efficient strategy allowing the selective modification at the primary alcohol position of this natural product. Using appropriate protection/deprotection sequences, we prepared by hemisynthesis several triazoles linked to the oleuropein core, as representative examples for the development of such an approach.     

六苄基六氮杂异伍兹烷五种氢解脱苄化合物的合成及工业制备

综述了六苄基六氮杂异伍兹烷(HBIW)五种氢解脱苄化合物的合成条件和工业制备工艺。这五种化合物是:四乙酰基二苄基六氮杂异伍兹烷(TADBIW)、四乙酰基二甲酰基六氮杂异伍兹烷(TADFIW)、四乙酰基六氮杂异伍兹烷(TAIW)、四乙酰基二乙基六氮杂异伍兹烷(TADEIW)和六乙酰基六氮杂异伍兹烷(HAIW)。其中的TADBIW系由HBIW经一次氢解合成,其它四种都系由HBIW经两次氢解合成。HBIW的这五种氢解脱苄化合物均可经硝解合成六硝基六氮杂异伍兹烷(HNIW)。另外,本文总结了HBIW及其五种氢解脱苄产物的红外、核磁和质谱数据及它们的基本性能参数。     

六苄基六氦杂异伍兹烷五种氢解脱苄化合物的合成及工业制备

综述了六苄基六氮杂异伍兹烷（HBIW）五种氢解脱苄化合物的合成条件和工业制备工艺。这五种化合物是：四乙酰基二苄基六氮杂异伍兹烷（TADBIW）、四乙酰基二甲酰基六氮杂异伍兹烷（TADFIW）、四乙酰基六氮杂异伍兹烷（TAIW）、四乙酰基二乙基六氮杂异伍兹烷（TADEIW）和六乙酰基六氮杂异伍兹烷（HAIW）。其中的TADBIW系由HBIW经一次氢解合成，其它四种都系由HBIW经两次氢解合成。HBIW的这五种氢解脱苄化合物均可经硝解合成六硝基六氮杂异伍兹烷（HNIW）。另外，本文总结了HBIW及其五种氢解脱苄产物的红外、核磁和质谱数据及它们的基本性能参数。     

Fast deprotection of phenoxy benzyl ethers in transfer hydrogenation assisted by microwave

Phenoxy benzyl ethers are easily and quickly deprotected in the presence of ammonium formate and microencapsulated Pd(0)EnCat with the assistance of microwave irradiation. This procedure can be applied in the presence of other functional groups as well. The described protocol is particularly convenient for the preparation in a parallel and automatic fashion of libraries of compounds possessing a phenol type moiety.